The present invention pertains to an improved towed sonar line array.
Towed sonar line arrays are very efficient listening devices. These line arrays have discrete transducers which are spaced along the array and are connected to processing apparatus aboard the towing vehicle. It is important that these transducers, which are the listening elements, are maintained in a predetermined spacing as the array undergoes the dynamic towing operation. During this operation there is considerable stress on the array and the tendency is to elongate which results in inaccurate data being received at the listening apparatus.
Since the transducers are listening for sound from far field source it is imperative that the array induced noises be minimized. Two major induced noises are vibration induced noise, which is generated primarily at the down slope of the line array from the towing vessel to some depth, and the flow noise which occurs primarily along the straighter portion of the line array extending beyond the sloping portion of the line array. The vibration noise propagating into the array from the downward portion of the line array is sometimes referred to as strumming, and the flow induced noise along the remainder of the line array is due to turbulent flow immediately adjacent to the exterior surface of the line array. These induced noises have been troublesome for some time because of the prior art configurations and materials utilized. A common material utilized in the acoustic envelope of prior art sonar line arrays is polyvinyl chloride. The polyvinyl chloride has not had the radial compliance nor the damping characteristics that are necessary to minimize the self induced noise problems. The polyvinyl chloride is especially undesirable at low temperatures, such as those found in the Arctic.
Another problem with sonar line arrays is maintaining the longitudinal spacing between the transducers. In the past longitudinal fiber ribbons have been used to carry the longitudinal load. These ribbons result in unacceptable kinking during the construction. It is essential that the transducers be in their predetermined spacing during the towing operation.